Grinding tools to grind essentially cylindrical or other rotatable cutting tools have been previously proposed. One such grinding machine is described in U.S. Pat. No. 3,680,263, Johnson, in which a grinding head is provided carrying a grinding wheel or grinding disk. The machine is suitable for grinding the end cutting teeth in tools of the ball nose end mill types, and tools which have spiral flutes and end cutting teeth, which are jointed to the spiral flutes. The grinding head is fixed with respect to a vertical axis, that is, is not rotatable with respect thereto. The took, which is clamped in a suitable receiving spindle or chuck, is rotated by rotating the chuck. During the grinding operation, the cutting edges of the end faces, that is, of the end cutting teeth, can be ground, starting from the axis of the cutting tool and progressing towards the circumference of the workpiece or cutting tool.
This machine is not capable of also grinding the spiral grooves or flutes located at the circumference of the shank of the cutting tool; likewise, such grooves or flutes cannot be made in a solid cylindrical cutter which has end cutting teeth. It is thus not possible to prepare, by grinding, flutes or grooves to remove cutting chips by grinding the flutes or grooves, spirally, in a solid shank element. It is also not possible to grind a clearance angle on the cylindrical cutting surfaces, and thereafter to grind the edges in the radial region of the tools. In order to provide for complete sharpening of a milling cutter which has spiral flutes as well as end teeth, however, or to prepare spiral flutes, it is necessary to utilize various types of grinding machines, which requires repetitive clamping of the workpiece in various machines and subsequent careful alignment of the workpiece or cutting tool in the respective grinding machines.
U.S. Pat. No. 4,115,956 describes a cutting machine which is particularly adapted to grind cutting edges and clearance surfaces on cutting tools such as end mills and similar cutters. The machine is numerically controlled, that is, is program-controlled, and utilizes a cutter head which is rotatable about a vertical axis in order to increase the utility of the machine and to permit a larger number of cutting surfaces to be ground than prior machines. The increased versatility of the machine, however, requires complex construction thereof. All the grinding operations are carried out with a single grinding disk or grinding wheel which is located on the grinding head. Consequently, the positioning movement for the grinding head and for the single grinding disk thereon becomes complex; it is still very difficult to provide for grinding of a spirally grooved end and boring mill cutter at all cutting surfaces thereof.
The machine requires a cutting disk of complex shape, since various surfaces on the milling cutter to be ground have to be sharpened by the same cutter disk. Use of such a special cutter disk is expensive and not economical, both with respect to wear on the cutter disk as well as to its adjustment and positioning in the machine relative to the milling cutter which is to be sharpened. It is thus not possible to use standard cutter disks or cutting wheels which are stock articles of trade in the machine tool field.
It has previously been proposed to construct a numerically controlled machine tool sharpening grinder in which a grinding head has two grinding disks secured thereto, located in fixed distance, and fixed relative angular position opposite each other, which permit subdividing the grinding operations. A machine of this type, particularly designed for grinding of the cutting surfaces of end mills, does not permit, however, grinding all the cutting surfaces of complex cutter tools which cut at the end surfaces as well as the circumferential radial surfaces, unless a machine of this type can be constructed to operate about eight differently positioned axes of rotation or of reference. Construction of a machine with that many reference axes is extremely expensive and complex.